Oxidative treatment of petroleum distillate fuels containing olefinic unsaturated components

ABSTRACT

PETROLEUM DISTILLATE FUELS CONTAINING OLEFINS AND DISSOLVED MOLECULAR OXYGEN ARE TREATED WITH FROM 0.1 TO 1.0 WT. PERCENT OF AT LEAST ONE ARYLHYDRAZONE, PREFERABLY THE ARYLHYDRAZONE OF A CYCLO ALIPHATIC SATURATED HYDROCARBON KETONE, AFTER WHICH BOTH THE INSOLUBLE AND SOLUBLE GUMS ARE SEPARATED FROM THE SO TREATED FUELS.

United States Patent ice US. Cl. 44-64 ABSTRACT OF THE DISCLOSUREPetroleum distillate fuels containing olefins and dissolved molecularoxygen are treated with from 0.1 to 1.0 wt. percent of at least onearylhydrazone, preferably the arylhydrazone of a cyclo aliphaticsaturated hydrocarbon ketone, after which both the insoluble and solublegums are separated from the so treated fuels.

The present invention relates to the oxidative treatment of petroleumdistillate fuels containing olefinic unsaturated components and, moreparticularly, relates to the stabilization of such fuels especiallythose having boiling points within the range of between about 75 F. andabout 750 F. whereby it is possible to improve the stabil ity of suchfuels and to thus greatly alleviate the gum forming tendencies of suchfuels when stored or stand ing under atmospheric conditions and incontact with the atmosphere.

The petroleum industry has long recognized the instability of distillatepetroleum fuels, boiling between about 75 F. and about 750 F. or havingboiling ranges within this range, largely due to the presence ofolefinic unsaturated components in such fuels. This constitutes aserious problem in connection with the use, handling, and storage of thefuels because the unstable constituents chief among which are the monoand diolefinic components, tend to gradually oxidize or otherwise react.For example, polymerization or copolymerization occurs during storage toform gums, sludges, and/or sediments which either precipitate out of thefuel of which remain in solution in the fuel and are later depositedthrough vaporization or combustion of the fuels in fuel lines,carburetors, pistons, cylinder walls and other surfaces in internalcombustion engines thus causing breakdown in lubrication and a generalgumming up in internal combustion engines. Such clogging and depositionof either precipitate or dissolved gums or sludge which have formed as aresult of the co-oxidation or oxidation of the olefinic componentsnecessitates the disassembling of the engine and the cleaning of allmoving parts including carburetors, fuel lines, filters and the like.This becomes an extremely expensive operation and entails time consumingeffort. In the past, this has sometimes been controlled to some extentthrough the addition of antioxidants to the petroleum distillate fuelscontaining the olefinic components.

The present invention provides a new and improved method of treatment ofsuch unsaturated petroleum distillate fuels in order to accelerate undercontrolled proce dures and conditions, the formation of gum and sludgewhich is thought to be brought about by polymerization andcopolymerization of the olefinic components through the peroxidationand/or oxidation, of these components whereby both soluble and insolublegums and sludges are formed. It is, of course, readily apparent thatonce the major portion of those olefinic components having the greatesttendency towards oxidative polymerization and/ or copolymerization areremoved as insoluble solids by centrifugation and the like or byvaporization to isolate 3,597,173 Patented Aug. 3, 1971 the potentialgums which are dissolved in the fuels, the resultant distillate fuel is,to a large extent, stabilized.

The novel treatment involves the addition of between about 0.1% andabout 1.0%, preferably between about 0.3 Wt. percent and about 0.6 Wt.percent of one or more specific arylhydrazones. Another requirement isthat mo lecular oxygen, i.e., air, be either dissolved in the fuels sotreated or at least the fuels should be in contact with molecular oxygensuch as in the form of air. Depending upon the relative hydroperoxidicactivity of the particular hydrazone or hydrazones employed anddepending upon the temperature employed, which may range fromatmospheric up to about F. or thereabouts, the time of contact requiredto achieve substantial oxidative reaction of the olefinic components mayrange from about 30 minutes up to several hours, for example, up to 8 or50 hours or even longer. In general, however, atmospheric temperaturesand pressures are entirely suitable for effecting the oxidativepolymerization and/or copolymerization of the olefinic constituents. Amere settling operation followed by decantation, centrifugation, orfiltration will remove the solid gums thus leaving a fuel containingonly potential or dissolved gum. A subsequent atmospheric or vacuumdistillation, if convenience dictates, will result in a distillateproduct substantially free of both solid and dissolved gum. It has beenfound that fuels so treated are effectively stabilized against furtheroxidation. If necessary, prolonged periods of storage of the so treatedfuels in the presence of conventional antioxidants such as2,6-di-tertiary butyl phenol, p-amino phenol, di-phenylamine andN,N-di-secondarybutyl-p-phenylene diamine, when added in amounts up to.01 wt. percent, results in stable fuels over prolonged periods of time,i.e., of the order of many weeks and, in fact, months.

The arylhydrazones employed are those having the formula:

wherein R may be a C C saturated acyclic hydrocarbon radical such asmethyl, ethyl, isopropyl, propyl, butyl, isobutyl, octyl, iso-octyl,dodecyl and the like or may further be a C -C saturated cyclic aliphatichydrocarbon radical such as cyclopentyl, cyclohexyl, cycloheptyl and thelike, and aralkyl radical such as benzyl, phenethyl or an aryl radicalsuch as phenyl, naphthyl, or anthryl. R

may be the same as or different from R as above defined,

R and R may be jointly a C -C alkylene (cycloaliphatic) radical or R maybe hydrogen. It has been discovered, however, that R may not be an arylradical if R is also an aryl radical. The arylhydrazine reacted withthis ketonic or aldehydic compound must be an arylhydrazine such asphenylhydrazine, naphthylhydrazine, or anthrylhydrazine. Representativehydrazones employed are the phenylhydrazones of cyclohexanone,cyclopentanone, benzylaldehyde, para-tolyl aldehyde, dibenzyl ketone,acetophenone, 9-anthranaldehyde, l-naphthaldehyde, and Z-naphthaldehyde.The arylhydrazones may be formed by reacting the hydrazine with a mixedketoaldehyde such as pivalyl aldehyde, a dialdehyde such asphthalaldehyde, or a diketone such as cyclohexanedione orcyclopentanedione. As used in this description and accompanying claims,the definitions of R and R are intended to encompass the mixedketoaldehydes, the diketones, and the dialdehydes.

The oxidative treatment, involving the use of arylhydrazones as abovedescribed and defined, of the petroleum distillate fuels containingolefinic unsaturated components applies to a wide range of gasolines andheating oils. These may be derived from gas oils of any desired boilingrange through the conventional steam cracking, thermal cracking, orcatalytic cracking of the same. Almost any cracked naphtha or heatingoil contains considerable quantities of olefinic compounds. Theseolefinic compounds, depending upon the particular process by which thenaphtha was produced, can be either cyclic or acrylic in nature. Theycan be mono-olefinic or di-olefinic (either conjugated, nonconjugated,or of the allenic type). In some cases polymeric forms of olefins arepresent in the cracked naphthas as produced, generally in soluble form.Any of the cyclic or acyclic olefinic unsaturated compounds such asindene, or even styrene, will be effectively polymerized orcopolymerized through the novel arylhydrazone treatment hereindescribed. Typical olefins found in cracked naphthas and heating oilsinclude the following: Z-heXene, cyclohexene, indenc, 1,3-hexadiene,l-pentene and 4-methyl-2-hexene. Any number of these olefinicallyunsaturated compounds other than those specifically mentioned tend torender gasoline or heating oils unstable during storage.

Additionally, and depending upon the source of the crude oil which hasbeen used, these distillate fuels may also contain nitrogen compoundssuch as pyrroles, indoles, aliphatic amines and pyridines, disulfides,and finally mercaptans of both aliphatic and aromatic nature, Althoughit is not intended that the instant novel process be limited by anytheory, it is believed that substantial portions of these types ofimpurities also undergo oxidative reaction involving polymerizationand/or oxidative reaction involving copolymerization of these impuritieswith some of the olefinc components present and so are likewiseconverted into gums or sludges which can be removed in the same mannerand at the same time as the gums and sludges formed solely from theolefinic constituents.

The presence of other additives in the treated distillates such asantiknock agents, scavenging agents, dyes, antiicing agents, and solventoils in total additive concentra- 4 EXAMPLE 1 A heavy catalytic crackednaphtha of the type above stated, in aliquots, was treated with about 1wt. percent of a number of different phenylhydrazones under thetemperature and time conditions shown in Table I.

The first run shown in the table is a blank run involving no treatmentwith a phenylhydrazone and is shown for comparative purposes only. Thecomparative tests were carried out as follows:

A 500 cc., round bottom, 4-necked flask was equipped with a paddlestirrer, an overhead water-cooled condenser, a thermometer, and aself-sealing rubber cap. Molecular oxygen was supplied to the vesselfrom a partially filled polyethylene gas balloon, through a wet-test gasmeter through which oxygen was passed, connected to a drying towerpacked with a desiccating material such as Drierite (anhydrous magnesiumsulfate). There was then introduced into the reaction vessel through theneck of the flask 200 to 250 cc. of naphtha and 2 to 2.5 grams of theparticular phenylhydrazone, when used. The system was then purged withoxygen, sealed with the rubber cap, and the wet-test meter adjusted toZero volume when an equilibrium pressure was established. The reactionwas then started by rapid stirring and was allowed to proceed until nofurther oxygen consumption could be detected on the wet-test meter. Allexperiments were conducted at atmospheric pressure.

In the following tables, the column headed Existent Solid Gum and thecolumn headed Soluble Gum added together give the total gum formed inthe treating process; the existent gum being precipitated from thenaphtha and recovered by filtration and weighed in terms of milligramsper 100 cubic centimeters of naphtha and the potential gum being solublegum which was recovered after distilling to dryness and weighing thegum. These figures are also in terms of milligrams of gum per 100 cc. offeed.

TABLE I.PHENYLHYDRAZONE-CATALYZED DEGRADATION OF ACTUAL PETROLEUMFRACTIONS Total gum Amount Phcnylhydrazone Temp., Time, Existent SolubleFood in cc. derivative Grams hours solidgnm gum 1 Heavy catalyticnaphtha 2 200 25 -24 34 844 Do 200 Benzaldehyde... 2 25 90 562 1,383 200.do 2 70 666 1,521 200 Acetophenone 2 25 163 505 1, 004 200 do 2 25 71370 2,820 200 do 2 50 66 1, 647 3,266 200 Indanedione 2 25 170 544 1,757250 Cyclohexanonc 2.5 25 119 605 1,584 250 Cyclopentanone .c 2.5 25 69273 1, 041

l Mg./100 cc. of feed; 2 Blank run.

tion not exceeding 5 %by weight does not adversely affect At 25 C.,benzaldehyde phenylhydrazone and acetothe oxidative treatment witharylhydrazones for the purphenone phenylhydrazone increased existent gum11- to pose of forming gums. Conversely, the treatment with 17-fold andpotential gum 1.2- to 3.3-fold. When the arylhydrazones does notadversely affect the functioning temperature was increased to 50 C., noappreciable of the aforementioned conventional additives for their inincrease in gum was observed with benzaldehyde phenyltended purpose, sothat it is possible to successfully carry hydrazone but, withacetophenone phenylhydrazone, eX- out the oxidative gum formationoperation on either te gum Was increased 48-fold and potential gum wasfinished or unfinished gasolines or heating oils, which concreased4-fold. Indanedione phenylhydrazone, though wi th l fi i componentsconsiderably less reactive than benzaldehyde phenylhydra- Representativespecific types of naphthas and heating ZOI1e and acetophenonephenylhydrazone in the rate oils to which the invention applies areheavy catalytic Studles, Pr e a 15-f ld increase in existent gum andnaphthas, light catalytic naphthas, #2 heating oil and the a Increase inPotential1 gum after 170 hours 0f like. Typical and representativechemical and physical oxidation at 25 C. Similar results were obtainedwhen inspections of two such naphthas are as follows: cycloheXanOnephenylhydrazone and cyclopentanone phenylhydrazone were added to theheavy naphtha frac- Heavv L h tion. No appreciable reaction (gumformation) was obcatalytic catalytic naphtha naphtha served when eitherthe benzophenone phenylhydrazone or Gravity, A31 25 fl ne phnylhydrazone was employed as the ox1da- Initial boiling point, 0 F 43077 tion polymerization catalyst. Final boiling point, F. 650 430Research octane numben. 55 EXAMPLE 2 Wt. percent aromatics c. 47.1 11.3Wt. pelii'cent mono olefins-diolefins (cyclic plus 26 III a mannersimilar [0 that described in Example 1,

.3 57.8 w g rgent saturates (cyclic plus acyclic) 26.6 30. 9 a lightcatalytlf: naphtha haVmg the Inspect)? above stated was treated withvarious phenylhydrazones 1n the amount of about 1.0 wt. percent. TableII shows the temperature and time conditions employed and the amount ofsolid and soluble gum formed as a result of the treatment.

hydrazone of cyclohexanone proved to be highly effective in catalyzinggum formation of both the soluble and insoluble type.

TABLE II.PHENYLHYDRAZONE-CATALYZED DEGRADATION OF ACTUAL PETROLEUMFRACTIONS Table Gum Amount Derivative of Temp., Time, Existent SolubleFeed in cc. phenylhydrazone Grams C. hours solid gum gum Light catalyticnaphtha 25 -24 6. 6 308 Do 2 25 72 346 853 2 50 96 632 1,017 2 50 117524 1, 102 t 2. 4 25 70 678 200 Acetophenone 2 25 67 308 697 200Q-anthranaldehyde 4 3 25 115 825 250 cyclohexanone 2. 66 363 814 200 do2 25 71 560 1,361

1 Mg./100. 2 Blank run. 3 Recovered 2.1 grams para-nitro benzaldehydephenylhydrazone. 1 Recovered 3.0 grams Q-anthranaldehydephenylhydrazone.

Autoxidation of the light naphtha fraction in the pres- EXAMPLE 4 enceof benzaldehyde phenylhydrazone and acetophenone phenylhydrazoneproduced a 47- to 53-fold increase in existent gum and a 2.3- to2.6-fold increase in potential gum at 25 C. With benzaldehydephenylhydrazone at 50 C., existent gum was increased 80- to 105-fold andpotential gum was increased 3-fold. 9-anthranaldehyde phenylhydrazoneand n-nitrobenzaldehyde phenylhydrazone did not increase existent gumbut they did increase potential gum by a factor of 2 to 3. In thepresence of cyclohexanone phenylhydrazone existent gum was increased bya factor of 53 to 85 and potential gum was increased by a factor of 2.7to 4.4. These results were obtained after 66 to 71 hours of reaction.

The above data show that for the examples cited, cyclohexanonephenylhydrazone is the most effective catalyst. The data also show thatelectron withdrawing groups, e.g., nitro, attached to the nucleus of thephenylaldehyde phenylhydrazone, decrease phenylhydrazone reactivity andthat an increase in aromaticity of the aryl group of the aldehyde usedresults in a decrease in reactivity, i.e., benzaldehyde phenylhydrazoneand acetophenone phenylhydrazone are more effective catalysts than9-anthranaldehyde phenylhydrazone.

EXAMPLE 3 A regular commercially available catalytically crackedgasoline having a boiling range of 100-350 F. and a Research OctaneNumber of 87 and having a chemical composition of 45 wt. percent ofcyclic plus acyclic olefins and diolefins, wt. percent of aromatics and25 wt. percent of parafiins and naphthenes was treated withcyclohexanone phenylhydrazone in the manner described in Example 1.Table III shows the amount of precipitated gum and soluble gum obtainedin each case:

A mildly hydrotreated steam cracked naphtha of about 140 F. initialboiling point and about 480 F. final boiling point, having about 16 wt.percent total ole-finically unsaturated hydrocarbons, about 44 wt.percent of aromatics with the balance being parafiinic constituents, wasemployed.

300 cc. of this naphtha was treated in the manner described in Example 1at 25 C. for 47.0 hours with 3.0 grams of the phenylhydrazone derivativeof benzaldehyde. The reacted mixture was worked up and analyzed in thesame manner as described in Example 1.

The bromine number of the feedstock was 86.1 and the product, afterco-oxidation, had a bromine number of 80.0. The fresh naphtha contained42 mg. per 100 cc. of feed of solid gum and 2177 mg., on the same basis,of potential or soluble gum. The treated naphtha contained 922 mg. and4188 mg, respectively, of solid and soluble gum, on the same basis. Thisrepresents, by the treatment, a two-fold increase in soluble gum and a22-fold increase in solid or existent gum and gives a treated naphtha,after separating of both types of gum, of vastly increased stability instorage.

The arylhydrazones used in the instant novel process are readily formedby conventional processes. One process involves the reaction of a ketoneor an aldehyde with the particular arylhydrazine in equimolar amounts ina solvent such as ethanol for a period of time between about 1 and 24hours and at a temperature of between about 32 F. and about 212 F. Atrace of acetic acid or sulfuric acid is employed as the catalyst. Thesolidified arylhydrazone precipitates from the solution is collected byfiltration, dried, and is then ready for use in the instant novelprocess. Any conventional method may be employed in the production ofthe arylhydrazones and TABLE IIL-PHENYLHYDRAZONE-CATALYZED DEGRADATIONOF ACTUAL PETROLEUM FRACTIONS Total gum Existent Soluble AmountDerivative oi Temp, Time, solid (potential) Feed in 0.0. phenylhydrazoneGrams 0. hours gum gum 1 Regular gasoline 1 25 -24 6. 6 363 Do 25 140333 753 Do 25 51 122 766 1 Mg./100 cc. of feed. 7 Blank run.

a 0.5 wt. percent. 4 0.1 wt. percent.

In the presence of between about 0.1 and about 0.5 wt. percent ofcyclohexanone phenylhydrazone, potential gum was increased by a factorof 19 to 50 and existent gum was increased by a factor of about 2.

It will be seen that in this particular treatment of a regularcommercially available gasoline that the phenylrated herein byreference.

Having now thus fully described and illustrated the instant novelprocess, what is desired to be secured by Letters Patent is:

1. A process which comprises treating, in the liquid phase, a petroleumdistillate fuel containing olefinic unsaturated components, in thepresence of molecular oxygen, with between about 0.1 and 1.0 wt. percentof at least one phenylhydrazone selected from the group consisting ofthe phenylhydrazone of cyclopentanone, the phenylhydrazone ofcyclohexanone and the phenylhydrazone of acetophenone, and separatingthe resultant insoluble gums from the so treated fuel.

2.. A process as in claim 1 wherein the distillate fuel is a crackednaphtha boiling within the range between about 75 F. and about 750 F.

OTHER REFERENCES The Chemistry of Hydrazine Audrieth et al., Copyright,1951, John Wiley & Sons, Inc., pp. 226-227.

10 DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US.Cl. X.R.

